Janet Guffenbert, age 13, of Lancaster, Pa., for her question:

Why is lb. the abbreviated form of pound?

An abbreviation is a brief or shortened form of a word. As a rule it is a contraction of the word in which only a few of its letters are used. The abbreviated form of Wednesday is Wed., and Pa. is the proper abbreviation of Pennsylvania. Always remember to follow an abbreviation with a period, whether or not it occurs at the end of the sentence.

Since an abbreviation usually takes the first and perhaps one or more other letters from the original word, you would expect the shortened form of pound to be pd., but this is not so. Lb. is the abbreviated form for the pound weight and lbs. is short for pounds. The word pound is descended from the name of an old Anglo Saxon weight, and libra is the Latin name for a weight. For some strange reason we use the abbreviation of the Latin word for pound.